In the prior art, in the servers and the personal computers, in order to radiate the heat generated from the semiconductor element efficiently, the semiconductor element is connected to the heat spreader through the thermally conductive sheet. As the thermally conductive sheet, an indium sheet or the like is used, and the heat radiation member is formed of copper or the like which has high thermal conductivity.
However, the price of indium which is used as a material of the thermally conductive sheet is rising due to the increase of the demand, therefore there is fear to cause cost rising. Moreover, from a viewpoint of radiating efficiently the heat generated from the semiconductor element, the thermal conductivity of indium may not be high enough.
From such background, a technique in which carbon nanotubes are used as the material for the thermally conductive sheet has been proposed, the carbon nanotubes which have higher thermal conductivity than that of indium and can be formed with a lower cost.
A related art is disclosed in Japanese Laid-open Patent Publication No. 2011-204749, and Japanese Laid-open Patent Publication No. 2013-107781.